The Cobra and Huey helicopters were conducting a training exercise at the time of the crash according to defense officials

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Seven U.S. Marines died when two helicopters collided Wednesday night near Yuma, Arizona.

The crash occurred around 8 p.m. in a remote portion of the Yuma Training Range Complex officials said.

Marines Killed in Chopper Crash

Seven U.S. Marines were killed Feb. 23 during a training exercise in the desert near MCAS Yuma. First Lt Maureen Dooley spoke with NBC 7's Lea Sutton about the inherent risk faced by all Marines when training for combat (Published Monday, May 28, 2012)

There were no survivors.The identities of the seven killed have not been released pending formal notification of next of kin.

Marines Killed in Chopper Crash

Seven U.S. Marines were killed Feb. 23 during a training exercise in the desert near MCAS Yuma. First Lt Maureen Dooley spoke with NBC 7's Lea Sutton about the inherent risk faced by all Marines when training for combat (Published Monday, May 28, 2012)

Six of the Marines killed were from Camp Pendleton. One Marine was based at MCAS Yuma.

The cause of the crash is under investigation.

The crash happened west of the Chocolate Mountains in California, though the exact location hasn't been confirmed Capt. Staci Reidinger, director of public affairs at Marine Corps Air Station Yuma said.

"It's not in a populated area," she said.

The aircraft involved were an AH-1W Cobra (seen right) and a UH-1Y Huey (similar to the Venom pictured below left).

The Cobra is described as "the backbone" of the USMC attack helicopter fleet. The aircraft carries a pilot and a co-pilot/gunner.

The Huey, also called Venom and Super Huey, carries one or two pilots, plus crew chief and other crew members as the mission requires.

The 3rd Marine Airwing, headquartered at Miramar, provides "the aviation combat element for I Marine Expeditionary Force", according to the unit's website.

Defense officials initially said the Marines were from the 3rd Marine Airwing based out of MCAS Miramar.

At the time of the crash, the temperature was 69 degrees and there were clear skies with just a light, 7 mph, wind according to the official reading from MCAS Yuma.

Officials confirmed five Marines were in the Huey at the time of the collision. Two were in the Cobra.

USMC officials are being intentionally vague about the specifics of the crash and training that was being conducted out of sensitivity to the families.

They want to make sure families are properly notified before information is released that would lead people to which units and Marines may have been involved

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